Detailed explanation of methods to suppress battery thermal runaway

The process of battery charging and discharging is a process of short chemical reaction. Lead sulfate is lead oxide during charging, and lead oxide is reduced to lead sulfate during discharge. Lead sulfate is a substance that is very easy to crystallize. When the concentration of lead sulfate in the battery electrolyte solution is too high or the static time is too long, it will form small crystals. These small crystals will attract the surrounding sulfuric acid. Lead will form large inert crystals like a snowball. The crystallized lead sulfate can no longer be reduced to lead oxide during charging, it will also precipitate and adhere to the electrode plate, resulting in a reduction in the working area of u200bu200bthe electrode plate. This phenomenon is called sulfation, that is, aging. At this time, the capacity of the battery will gradually decrease until it becomes unusable. When a large amount of lead sulfate accumulates, it will attract lead acid particles to form lead branches, and the lead branches between the positive and negative electrodes will cause a short circuit in the battery. If there are gaps on the surface of the electrode plate or the sealed plastic shell, lead sulfate crystals will accumulate in these gaps, and expansion tension will appear, which will eventually cause the electrode plate to break off or the shell to rupture, causing irreparable physical damage to the battery. Therefore, an important mechanism leading to battery failure and damage is sulfation which cannot be prevented by the battery itself. As long as it is a lead-acid battery, sulfation will occur during use, but the lead-acid battery used in other fields has a longer life than the lead-acid battery used in electric bicycles. This is because of the lead-acid battery of electric bicycles. The battery has an environment that is easier to hydrochloride. The current when an electric bicycle is running at a speed of 20km/h is generally 4A, which is already higher than the working current of batteries used in other fields, while the working current of an overspeed and overload electric bicycle is even greater. Battery manufacturers conduct cycle life tests of 70% at 1C and 60% at 2C. After such a life test, there are many battery life that can reach 350 charge-discharge cycles, but the actual use effect is far different. This is because the high-current operation adds 50% of the depth of discharge, and the battery will accelerate the sulfation. The sufficient voltage of the lead-calcium alloy battery is higher, and the charging voltage of a 12V battery is generally greater than 16V. When the voltage of the charger is too low, it is easy to cause the unbalance of the battery. The reason is that the self-discharge of each cell of the battery cannot be absolutely equal, and the battery with a self-discharge greater than a little can not be fully charged every time it is charged with a constant voltage. Insufficient cells do not undergo gassing reaction, and the area of u200bu200bthe electrode plate contacting the electrolyte is relatively reduced, and the self-discharge will be reduced. At the same time, the charging voltage will increase and the cells that have reached a large charge will be more and more self-discharged each time. Can not be fully charged, and the more the battery is used, the smaller the battery, the long-term undercharged battery will fail due to sulfation. The above phenomenon will occur if the constant voltage value of the constant voltage charger is too low. If the constant voltage value is too high, the battery will be charged with a higher voltage and a smaller current for a long time to balance the self-discharge of the battery. Overcharging often requires high current and high voltage, and high current and high voltage will form strong side reactions that damage the positive plate of the battery and cause the battery to lose water. The use of high-voltage, high-current pulses can overcome the decline in battery acceptability caused by many reasons. Because of the use of pulses, after the high-current pulses disappear, the depolarization ability of the battery itself (or external conditions) is not Form a serious side reaction. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: How does BYD's blade battery perform at low temperatures?